Behaviors Analysis Of Composite Ground Under Flexible Foundation

Since its good economy and practicability, composite ground was widely used under the flexible foundation such as embankment foundation. Lots of research indicate that much difference exists in the composite ground under the flexible foundation and the rigid foundation, it will has big difference between the calculateld value and the measured one to apply the theory and the corresponding bearing capacity and settlement formula which is applicable to the rigid foundation, and the results tends to be insecurity. Therefore, it is necessary to further the research work about the behaviors of the composite ground under the flexible foundation. So based on the previous research, the mechanism, soil arching effect, settlement and design method of the composite ground under the flexible foundation was studied in this paper.Firstly, the mechanism and the pile-soil deformation characteristics of the composite ground under the flexible foundation was discussed in this paper from the combined action points of the whole system consistes of up and down section; Secondly, according to the mechanical deformation of the upper embankment, limit equilibrium theory was employed to derive the expression of the earth pressure acting on geogrid. With the horizontal reinforced cushion for research object, that it’s concave curve was assumed as a parabolic, based on the theory of elasticity, considering the static equilibrium and the compatibility of deformation as well as the supporting effect of soil between piles under the geogrid, a new calculation method of the pile-soil stress ratio of composite ground under the flexible foundation deducted; Then, considering the pile-soil relative sliding characteristics of composite ground under the flexible foundation, take the shear deformation characteristics of pile-soil interface into account, with the assumption of the displacement mode, equilibrium equation is established through considering the stress-deformation coordination of embankment, pile-soil reinforced area and underlying soils based on the typical element, the solutions for the settlement and stress ratio of pile-soil, which are used to characterize the behaviors of the composite ground is obtained; Finally, in view of the load carring characteristics of the composite ground under the flexible foundation such as embankment, using the ideas of settlement control, design method, the bearing capacity verify and stability analysis for the composite ground under the flexible foundation are summarized, in the hope of reference for relevant engineering practice.In this paper, the method to calculate the pile-soil stress ratio of composite ground under the flexible foundation, which has considered the stress redistribution phenomenon because of the soil arching effect and the supporting effect of the soil between piles for reinforced cushion; Meanwhile, the method of calculating the settlement of composite ground under the flexible foundation, which takes both the stress and deformation coupling of embankment, pile-soil reinforced area and underlying soils and the non-synchronized settlement of pile-soil at the same depth, as it accord with the mechanism and pile-soil interaction characteristics of composite ground under the flexible foundation, there will have a certain reference value to improve the calculating theory of composite ground under the flexible foundation.